1. Field of the Invention
This invention relates broadly to surgical devices. More particularly, this invention relates to devices for an over-the-guidewire exchange of one catheter for another in the human body.
2. State of the Art
Catheterization procedures are well known for diagnosis and therapy of lesions in the cardiovascular system. One such procedure is angioplasty, for eliminating or ameliorating the vascular blockage or constriction in blood vessels associated with supplying blood to the heart or other organs. In an angioplasty procedure, an expandable balloon carried by an elongated catheter is introduced into the arterial system of a patient and advanced until it is positioned in the region of the blockage or constriction. Once so positioned, the balloon is expanded by filling it with a liquid. In successful procedures, the expandable balloon presses outwardly against the walls of the artery and expands the artery to a degree to which the artery is either partially or completely reopened to blood flow.
Prior to initiating the angioplasty procedure, a guiding catheter is placed, typically via the femoral artery, into the aorta and its tip is engaged into the coronary arteries which branch from the aorta. Once placed, the guiding catheter acts as a conduit to access the coronary arteries with a guidewire and balloon catheter. The guiding catheter is a portion of plastic tubing having a length of about 95 centimeters, an inside diameter of about 2 millimeters, and an outside diameter of about 2.5 millimeters. A hemovalve, i.e., a valve preventing blood loss through the guiding catheter when a tubular conduit such as a balloon catheter is passed therethrough, is provided at the proximal end of the guiding catheter.
Then, external of the patient, the physician threads a guidewire through a balloon catheter. The guidewire is a piece metal wire, e.g., titanium or nickel-titanium alloy wire, approximately 175 centimeters in length, and about 0.25 to 0.46 millimeters in diameter. The soft distal tip of the guidewire is often shaped to form a xe2x80x9cJxe2x80x9d configuration. This xe2x80x9cJxe2x80x9d shape allows the physician to steer the guidewire by twisting its proximal end while advancing or retracting the guidewire. The balloon catheter is an elongate flexible plastic tubular member defining two longitudinal passages and having a balloon located at or adjacent its distal end. One longitudinal passageway defines a conduit through which the guidewire can be passed. The other longitudinal passage defines a conduit in fluid communication with the interior of the balloon and through which inflation fluid can be injected to inflate the balloon.
Among the types of balloon catheters is one in which the two longitudinal passages are generally side by side and parallel. In another type of balloon catheter, the two longitudinal passages are coaxial. In this latter type, the guidewire is passed down the inner passage and the inflation fluid is injected into the balloon via the outer passage. Balloon catheters, as well as associated apparatus and their method for use in angioplasty, are generally described in U.S. Pat. No. 5,040,548 to Yock, which is hereby incorporated by reference herein in its entirety.
The physician passes the guidewire through the appropriate one of the longitudinal passages in the balloon catheter, leaving a portion of the guidewire extending from the distal and proximal ends of the balloon catheter. This assembly is then inserted through the hemovalve and into the proximal end of the guiding catheter, distal end first. The assembly is inserted until the balloon which is attached at or near the distal end of the balloon catheter is near the distal end of the guiding catheter. At this point, the physician, while maintaining the balloon catheter stationary, pushes on the guidewire to advance it outwardly from the distal end of the guiding catheter.
The physician steers the guidewire into the chosen one of the coronary arteries, and advances it until it reaches a location of constriction which the physician desires to open. Carefully, the physician eases the distal end of the guidewire through the region of constriction until the guidewire tip is on the opposite side of the constriction relative to the guiding catheter.
With the guidewire held stationary, the physician advances the balloon catheter over the guidewire until it is located in the region of constriction of the artery. Then, with the balloon held stationary, inflation fluid is injected into the conduit which communicates with the balloon, causing it to inflate. Inflation of the balloon expands the walls of the artery in the region of constriction and, in successful procedures, opens the artery to sufficient blood flow.
Arteries vary in size, and therefore balloon catheters having balloons of different sizes are provided for selection by the physician. These balloons, when inflated, range from about 1.5 millimeters to about 4 millimeters in diameter. Sometimes, it is necessary for the physician to use more than one balloon to open an artery, as in some instances, the chosen balloon may be too large to be advanced into the constricted area, or in other instances, the first chosen balloon size, even when inflated, is not large enough to open the constricted area to the degree desired. In such cases, it is necessary to exchange one balloon catheter for another during the same angioplasty procedure.
In order to accomplish this exchange, the guidewire is left in place, and the balloon catheter is withdrawn entirely from the guiding catheter until it is completely disengaged from the proximal end of the guidewire. A new balloon catheter, having a different sized balloon, is then reinserted over the guidewire and advanced back to the location of the constricted area, where it is used to effect the desired result.
It is highly desirable to leave the guidewire in position; i.e., once the guidewire is passed through the constricted area, preferably the guidewire remains extending through the constriction for the duration of the angioplasty procedure. This means that the guidewire must remain in place even during the exchange of balloon catheters. The reason for this is that when a foreign object, such as the guidewire, is introduced into an artery, the artery walls sometimes go into spasm, and constrict the artery generally along a substantial portion of its length. If the artery tends to contract in this way, removal of the guidewire while the artery is so contracted will sometimes render it virtually impossible to reinsert the guidewire through the contracted artery.
Withdrawal of the balloon catheter without dislocating the guidewire is a difficult and cumbersome procedure, requiring both a second individual, in addition to the physician, and the attachment of a removable extension to the proximal end of the guidewire. Attachment of the extension to the guidewire during withdrawal of the balloon catheter is necessary because, if the balloon catheter were withdrawn over the proximal end of the guidewire, there would be no way that the guidewire could be manually held stationary. The extension is required to provide a proximal end of the guidewire which will extend outwardly from the proximal end of the balloon catheter even when the balloon catheter is entirely withdrawn from the patient. Even with the extension, the physician must enlist the aid of an assistant to manually hold stationary the proximal end of the guidewire, preventing guidewire movement, while the physician withdraws one balloon catheter and inserts a replacement balloon catheter. This is a cumbersome and awkward procedure at best.
One solution to this difficult procedure is provided in U.S. Pat. No. 4,762,129 to Bonzel. Bonzel discloses a balloon catheter having a single lumen for inflation fluid and a balloon at the distal end of the catheter. The balloon has two passages: a first passage in fluid communication with the lumen of the balloon catheter to inflate the balloon and a second passage for receiving a guidewire therethrough. A guidewire extends externally alongside the balloon catheter and passes through the second passage and beyond the distal end of the balloon. As a result, once the distal end of the guidewire is passed through the vascular constriction, the proximal end of the guidewire may be manually held in position and the balloon may ride over the guidewire into the constriction. If needed, the balloon catheter can be withdrawn over the guidewire and a new balloon catheter may then be advanced over the guidewire to the locus of constriction. Nevertheless, the Bonzel device has several serious drawbacks. First, as hemovalves are generally designed to have a single tubular conduit extend therethrough, the geometry of the side-by-side extension of both the guidewire and the balloon catheter through the hemovalve prevents a fluid tight seal from forming about the balloon catheter-and guidewire. Therefore, use of the Bonzel apparatus results in increased blood loss from the patient. Second, the device requires substantially constant fluoroscopy or x-ray use, as the physician must be careful not to proximally displace the guidewire relative to the balloon such that guidewire is withdrawn from the second passage of the balloon. It will be appreciated that if the guidewire is completely removed from the second passage of the balloon while the guidewire and balloon catheter are located in situ, it is nearly impossible to reinsert the guidewire therethrough. Third, if the physician desires to exchange one guidewire for another (e.g., a stiffer guidewire for a more flexible guidewire), which is possible with balloon catheters having two conduits provided therein, the physician similarly faces the problem of not being able to insert the new guidewire through the second passage of the balloon. As such, the physician is limited to using the guidewire with which he or she began the interventional or diagnostic procedure.
A second solution is provided in co-invented U.S. Pat. No. 5,269,759 to Hernandez et al. which discloses an exchange device having a magnetic element and a guidewire provided with a magnetic portion. Magnetic forces are able to hold the guidewire fixed relative to the exchange device, permitting a first balloon to be withdrawn over the guidewire, and a second balloon to be advanced in replacement. However, the magnetic exchange device also has several drawbacks. First, it requires the use of high cost guidewires having magnetic elements. Second, magnetic guidewires tend to be more fragile than other guidewires due to undercuts in the guidewires for magnet placement. Third, magnetic guidewires have relatively poor steerability. Fourth, magnetic wires are more corrosive than non-magnetic guidewires.
Yet another solution is provided in U.S. Pat. No. 5,827,241 to Douk et al., which is hereby incorporated by reference herein in its entirety, in which it is disclosed that the position of a guidewire within the body can be maintained by constraining coextensive segments of the catheter and the guidewire in a non-linear configuration outside the body. The non-linear configuration is such that when the catheter is moved relative to the guidewire, the frictional force between the catheter and the guidewire is less than the force required to move the guidewire through the non-linear configuration. Therefore, as the catheter is advanced or withdrawn from the body, axial movement of the guidewire relative to the catheter is inhibited. While This teaching appears to suggest a good solution, it has not been commercially exploited due to the difficulties in implementing the teaching in a suitable device which quickly, easily and inexpensively plastically deforms the guidewire such that the catheter can then be moved relative thereto.
It is therefore an object of the invention to provide an exchange device which constrains coextensive segments of a catheter and a guidewire in a non-linear configuration.
It is an another object of the invention to provide an exchange device which plastically deforms the guidewire.
It is also an object of the invention to provide an exchange device which is unobtrusive and may be positioned adjacent the surgical field.
It is a further object of the invention to provide an exchange device which is easy to use.
It is yet another object of the invention to provide an exchange device which is relatively inexpensive to manufacture and disposable.
In accord with these objects, which will be discussed in detail below, a mechanical rapid exchange device is provided which plastically deforms a guidewire and constrains the guidewire in a non-linear configuration such that a catheter may be moved relatively proximally or distally over the guidewire to facilitate catheter exchange. The device generally includes a housing having a channel along a face of one side of the housing, a center punch movable between a first position in which the center punch is located substantially to one side of the channel and a second position in which it extends at least partially into the channel, two lateral punches movable between a respective first position in which they are located to the other side of the channel and a respective second position in which they extend at least partially into the channel. The device also includes a handle attached via levers to the lateral punches such that when the handle assembly is actuated, the lateral punches are moved into the second position. A plastically deformable support tube extendable over a portion of a guidewire and positionable within the channel is also provided.
In use, the plastically deformable support tube is positioned over an exterior portion of the guidewire (outside the human body), and the support tube is then positioned within the channel. The center punch is then moved into the channel and into its second position, i.e., against the support tube, and locked in position. The handle is next actuated, such that the lateral punches enter the channel from the side opposite the center punch and bend the support tube and guidewire about the center punch such that the support tube and guidewire are each plastically deformed into a non-linear configuration. When the handle is returned to its linear position, the lateral punches return to a position outside the channel, and the center punch, locked in position, prevents the deformed support tube from sliding axially within the channel of the housing. The non-linear configuration of the support tube is shaped such that when a catheter, e.g., a balloon catheter, is moved over the guidewire and through the support tube, the frictional force between the catheter and the guidewire is less than the force required to move the plastically deformed guidewire through the stationary support tube. Therefore, as the catheter is advanced or withdrawn through the support tube, axial movement of the guidewire relative to the support tube is prevented. A catheter may then be fed over the guidewire and into the support tube, i.e., between the support tube and the guidewire, while the guidewire is held in position by a physician or an assistant who holds the housing of the device. As such, withdrawing of a catheter over the guidewire and placement of a new catheter over the guidewire is facilitated.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.